Baseline predictors of worsening apathy in Parkinson's disease: A prospective longitudinal study

• We examine the baseline predictors of apathy in Parkinson's disease over 18 months.
• Individual trajectories of apathy symptom severity were highly variable.
• Gender, education, depression and functional status predicted apathy progression.

IntroductionApathy is one of the most common behavioural disorders in Parkinson's disease (PD) and contributes significantly to a reduced quality of life in PD patients.MethodsWe conducted a prospective longitudinal study of 89 mild PD patients over 18 months, measuring apathy symptoms at 6-monthly intervals using the Starkstein Apathy Scale, as well as measures of motor and non-motor symptoms, cognitive function, and functional disability at baseline. Mixed-effects models were used to characterise the individual trajectories of apathy symptom severity, and linear regression with stepwise elimination procedure was used to select significant baseline predictors.ResultsClinically significant levels of apathy were present in 42.7% of our sample at baseline, with symptom severity remaining relatively stable on average over the course of 18 months. Male gender, lower educational attainment, higher depression symptom severity, more severe functional disability, and the presence of dyskinesias at study entry predicted increasing apathy over the subsequent 18 months.ConclusionsPatients with these factors are at risk for progression of apathy, which may be prevented by treating depression and functional disability. Further studies are needed to address both the specific neurobiological pathways and psychosocial factors underpinning apathy in PD.